The invention is based on a hybrid circuit breaker.
The document EP 0 847 586 B1 discloses a hybrid circuit breaker which can be used in an electrical high-voltage network. This hybrid circuit breaker has two series-connected arcing chambers, a first of which is filled with SF6 gas as an arc extinguishing and insulating medium, and a second of which is in the form of a vacuum switching chamber. The second arcing chamber is surrounded by SF6 gas on the outside. The main contacts in the two arcing chambers are operated simultaneously via a lever transmission from a common drive. Both arcing chambers have a power current path, in which the consumable main contacts are located, and a rated current path in parallel with it, with this rated current path having only a single interruption point. On disconnection, the rated current path is always interrupted first, after which the current to be disconnected commutates onto the power current path. The power current path then continues to carry the current until it is definitively disconnected.
In this hybrid circuit breaker, the arc which always occurs in the vacuum switching chamber during disconnection burns for approximately the same time period as in the gas-filled first arcing chamber, which means that the main contacts in the vacuum switching chamber are subjected to a comparatively high and long-lasting current load and, linked to this, a high wear rate, which means that maintenance work has to be carried out comparatively frequently, as a result of which the availability of the hybrid circuit breaker is limited. This hybrid circuit breaker requires a comparatively large amount of drive energy since, depending on the switching principle used in the gas-filled first arcing chamber, the drive has to produce all or part of the high gas pressure required for intensively blowing out the arc. Such a drive, which is designed to be particularly powerful, is comparatively expensive. In this switch, the returning voltage is distributed capacitively between the two arcing chambers, with the intrinsic capacitances of the arcing chambers being the critical factor.
Laid-open specification DE 4 427 163 A1 discloses a compressed-gas circuit breaker whose arcing chamber has two main contacts which move in opposite directions. Part of the pressurized gas for blowing out the arc is produced by the arc itself and is stored in a storage volume, while the rest is produced in a piston-cylinder arrangement, depending on the movement of the main contacts, and, when required, this other part flows through the storage volume and blows out the arc. In this compressed-gas circuit breaker, the aim is for the arc to be blown out intensively, and this requires a comparatively high arc extinguishing gas pressure. The drive for the compressed-gas circuit breaker must therefore be powerful in order to allow the main contacts to move against this comparatively high arc extinguishing gas pressure.
In the known hybrid circuit breakers and conventional circuit breakers, the aim is always for the arc to be blown out as intensively as possible in the arcing chamber which is generally filled with a gaseous insulating and arc extinguishing medium. This intensive blowing is necessary in order to achieve good arc cooling and to ensure that the arc is extinguished properly, and that ionized gases and erosion particles are very rapidly removed from the extinguishing path. Once the arc has been extinguished, a major portion of the returning voltage is borne by this extinguishing path from the start. As a rule, such intensive blowing is achieved only if the flow rate of the blowing medium is in the supersonic speed range.
The invention, achieves the object of providing a hybrid circuit breaker which can be produced economically and which has high availability, and of specifying a method for its operation.
In this hybrid circuit breaker the first, steep rise in the returning voltage is borne essentially by the second arcing chamber, which is in the form of a vacuum switching chamber. Accordingly, the dielectric recovery of the extinguishing path in the first arcing chamber may take place comparatively slowly, which means that the blowing in the first arcing chamber may be considerably weaker than in conventional circuit breakers. Considerably less energy thus needs to be consumed to provide the pressurized gas required for blowing out the arc.
The advantages achieved by the invention are that the hybrid circuit breaker can be equipped with a considerably weaker and thus more economic drive for the same power switching capacity. Furthermore, the pressures which occur in the first arcing chamber in this hybrid circuit breaker are considerably lower than in conventional circuit breakers, so that the insulating tube and the other parts that are subjected to pressure can be designed for reduced loads as well, thus making it possible to design the hybrid circuit breaker to be more economic. Furthermore, it is advantageous that the flow rate of the gas which cools the arc in the first arcing chamber may be in the subsonic range since the blowing required in this case is considerably less intensive and, in consequence, the amount of pressurized gas that needs to be provided for blowing can be kept comparatively small.
A further advantage is that the main contacts in the second arcing chamber which, in this case, is in the form of a vacuum switching chamber have a longer life owing to the shorter duration of the current load during disconnection, and this results in improved operational availability of the hybrid circuit breaker. The time delay in the disconnection movement of the second arcing chamber in comparison to the first has the major advantage when asymmetric short-circuit currents are being disconnected that the second arcing chamber is loaded with considerably lower peak currents, since the asymmetry of the short-circuit currents decays even further during this delay time. If the second arcing chamber is in the form of a vacuum switching chamber, then this has a particularly advantageous effect on the life of the contacts.
The hybrid circuit breaker is provided with at least two series-connected arcing chambers which are operated by a common drive or by separate drives and are filled with different arc extinguishing media, wherein the arc extinguishing and insulating medium in the first arcing chamber surrounds the second arcing chamber in an insulating manner. Means are provided which ensure that the movement of the first arcing chamber leads the movement of the second arcing chamber during a disconnection process. A gas or a gas mixture is used as the arc extinguishing and insulating medium in the first arcing chamber. At least one vacuum switching chamber is provided as the second arcing chamber. However, other switching principles may also be used for the second arcing chamber, and, in particular, the second arcing chamber may also be in the form of a TVG (Triggered Vacuum Gap).